This invention relates to air distribution systems and, more particularly, to a thermostatic control usable in such systems.
Variable air volume distribution systems have gained acceptance in the air distribution field. Such systems are adapted tp provide different volumes of conditioned air to achieve particular temperatures in areas being serviced, thus the name variable air volume systems. Some systems go a step further and are adapted to provide a constant volume flow of air at that particular volume selected to achieve a given temperature condition. These are referred to in the air distribution field as constant variable volume systems. This invention is concerned with such systems.
Most often the interior spaces of a building are heated year-round by lighting and to a lesser degree, by people and heat loss from other electrical apparatus, and it is necessary to remove heat through the introduction of cold air. There are, of course, applications where the building interior will be furnished with hot air. The desirability of constant variable volume air delivery systems in such cooling, and/or heating, installations has been well recognized and the problem is to achieve overall control taking into account variations in the flow volume of delivery air to and variances in temperature in the room being serviced. This invention is concerned with that problem.
Conventional control thermostats usually provide either heating or cooling control, i.e. in an air system they pg,3 regulate the volume of air being introduced into the room as a percentage of available air capacity starting from a base point. For example, a thermostat set at 74.degree. F. may call for 50% more cooling air if the temperature rises to 75.degree. F. and 100% more cooling air if the temperature rises to 76.degree. F. In a heating application the same is true as the demand for hot air increases. Generally, in order to provide heating and cooling in the same system two thermostats have been required; calibration of the two thermostats is extremely difficult and in most instances overlap of the control function between the two thermostats cannot be avoided. In its more specific aspects, this invention is also concerned with this problem of providing continuous heating and cooling capability in a single control.